The present invention relates to a magneto-optical recording medium which can carry out magneto-optical recording and/or reproducing, and to an optical head device in which an objective lens is installed in a slider.
Optical disks, such as phase-change-type optical disks and magneto-optical disks, that are rewritable recording media with a large capacity have received much attention as a recording media for computers. The phase-change-type optical disks, typically including DVD-RAMs, and the magneto-optical disks, typically including AS-MOs, have been under development in order to achieve higher density recording with a larger capacity.
With respect to recording systems for magneto-optical disks, there have been known a light-intensity-modulation recording system in which the intensity of a laser light beam released from a laser light source such as a laser diode is changed and a magnetic-field-modulation recording system in which the intensity of a magnetic field generated by a magnetic head is changed; and either of these is used to carry out information recording. In the magnetic-field-modulation recording system, a floating-slider-type magnetic head or a sliding-slider-type magnetic head, which is used for recording and reproducing a magnetic disk, is also used for a magneto-optical disk. The magneto-optical disk has a layer construction including at least a substrate and a recording layer, and, for example, the floating-slider-type magnetic head is placed on a side closer to the recording layer. Upon recording and reproducing that requires a reproducing magnetic field, the slider is allowed to float above a disk face in the proximity thereof by an air flow that is generated in response to rotation of the magneto-optical disk, and after the slider has been shifted to a desired position above the magneto-optical disk, a magnetic field is applied thereto.
In the case of the above-mentioned magnetic head of a floating-slider type, the slider is maintained in a floating state while the magneto-optical disk is in rotation. However, even in such a floating state, when dusts, stains, etc. adhere to the disk surface, or when the disk has a warp, the stable floating state of the slider tends to deteriorate, with the result that the slider collides with the disk surface, causing damages to the disk surface. Moreover, the collision or crash of the magnetic head onto the disk surface might further damage a supporting mechanism for the magnetic head. Also in the case of the magnetic head of a sliding-slider type, when a sliding frictional force between the slider and the disk is not sufficient, the slider tends to jump, causing the possibility of scratches on the disk surface. Moreover, there is a possibility that a stable sliding operation with a constant speed is not available.
In order to avoid these problems, Japanese Patent Applications Laid-Open Nos. 6-176353 (1994), 7-254180 (1995) and 7-334865 (1995) have proposed magneto-optical recording media that are provided with a lubricating protective layer on the surface of a recording layer, that is, on the surface opposite to the substrate. The application of the lubricating protective layer minimizes a frictional force between the slider and the disk surface, thereby making it possible to prevent scratching even in the event of contact and collision and consequently to achieve a stable operation.
In recent years, a technique has been reported in which light-intensity-modulation recording or magnetic-field-modulation recording is carried out on a magneto-optical disk by using an optical head of a floating-slider type or a sliding-slider type. With respect to such an optical head of the slider type, various constructions have been proposed; and for example, some of them have a construction in which: an optical lens is installed on a slider, and a laser light beam, which is released toward a prism that operates in a manner so as to follow the slider, is allowed to pass through the optical lens and applied onto the disk surface.
In the same manner as the aforementioned magnetic head, the optical head of the slider type having the above-mentioned construction is susceptible to scratches on the disk surface due to degradation of the floating stability caused by dusts, stains, a warp in the disk, etc., when it is allowed to float above the disk surface by an air flow. Moreover, it is also susceptible to scratches on the disk surface due to degradation of the travelling stability caused by dusts, stains, a warp in the disk, etc., when it is allowed to slide on the disk surface. Furthermore, the supporting mechanism of the optical head might be damaged due to contact, collisions, etc. of the head onto the disk surface.
Generally, upon recording and/or reproducing of a magneto-optical disk, a laser light beam is made incident on a side closer to the substrate of the disk. Therefore, the optical head of the slider type is placed on the substrate. In the magneto-optical disks disclosed by the aforementioned Japanese Patent Applications Laid-Open Nos. 6-176353 (1994), 7-254180 (1995) and 7-334865 (1995), since the lubricating protective layer is formed on the surface of the recording layer opposite to the substrate, the resulting problem is that it is not possible to prevent scratches on the disk surface caused by the optical head of the slider type. Moreover, since the optical head requires a positional controlling operation with higher precision and has quicker movements as compared with the magnetic head, the resulting problem is that scratches on the disk surface and damages to the optical head tend to occur.
The present invention has been devised to solve the above-mentioned problems, and its objective is to provide a magneto-optical recording medium which can prevent scratches on the disk surface caused by a slider-type optical head, and improve the floating stability and travelling stability of the optical head.
The magneto-optical medium of the present invention is characterized by comprising: a substrate; a recording layer, formed on the substrate, for recording information; a first lubricating protective layer formed on the recording layer; and a second lubricating protective layer having a transparent/translucent property, being formed on a face of the substrate opposite to the recording layer. In the present invention, the transparent/translucent lubricating protective layer is placed on the same side that the optical head is located on in a magneto-optical recording medium of a type in which a light beam is projected from a side closer to the substrate. Therefore, upon carrying out recording/reproducing of information on the magneto-optical recording medium by using an optical head of a slider type such as a floating-type slider or a sliding-type slider, when the slider of the optical head is allowed to float above the lubricating protective layer in the proximity thereof, superior floating stability is achieved, and when it is allowed to slide on the lubricating protective layer, the sliding frictional force is minimized so that higher travelling stability is achieved. Moreover, since the lubricating protective layer minimizes the impact at the time when the slider contacts or collides with it, it is possible to prevent scratches on the disk surface.
The magneto-optical recording medium of the present invention is characterized by comprising: a substrate; a recording layer, formed on the substrate, for recording information; and a lubricating protective layer having a transparent/translucent property, being formed on the recording layer.
In the present invention, the transparent/translucent lubricating protective layer is placed on the same side that the optical head is located on in a magneto-optical recording medium of a type in which a light beam is made incident on a side closer to the recording layer. Therefore, when the slider of the optical head is allowed to float above the lubricating protective layer in the proximity thereof, superior floating stability is achieved, and when it is allowed to slide on the lubricating protective layer, the sliding frictional force is minimized so that higher travelling stability is achieved. Moreover, since the lubricating protective layer minimizes the impact at the time when the slider contacts or collides with it, it is possible to prevent scratches on the disk surface.
The magneto-optical recording medium of the present invention is characterized in that the transparent/translucent lubricating protective layer is a mixed lubricating layer which is made by mixing at least a transparent/translucent lubricant with a transparent/translucent resin.
In the present invention, a resin layer, which has been made by mixing at least a transparent/translucent lubricant with a transparent/translucent resin serving as a base material at a predetermined ratio, is placed on the same side that the optical head of a magneto-optical recording medium is located on. Therefore, it is possible to maintain superior floating stability and travelling stability in the optical head.
The magneto-optical recording medium of the present invention is characterized in that the transparent/translucent lubricating protective layer is provided with a resin layer made of a transparent/translucent resin and a lubricant layer that is made of a transparent/translucent lubricant, and formed as an outermost layer.
In the present invention, the lubricating protective layer is placed on the same side that the optical head of the magneto-optical recording medium is located on. Therefore, the substrate or the recording layer is protected by the resin layer so that the floating stability and the travelling stability of the optical head are improved by the lubricant layer.
The magneto-optical recording medium of the present invention is characterized in that the transparent/translucent lubricating protective layer is provided with a mixed lubricating layer made by mixing at least a transparent/translucent lubricant with a transparent/translucent resin, and a lubricant layer that is made of a transparent/translucent lubricant, and formed as an outermost layer.
Therefore, since the mixed lubricating layer and the lubricant layer are stacked, it is possible to further improve the floating stability and the travelling stability of the optical head.
The magneto-optical recording medium of the present invention is characterized in that at least one portion of the substrate is made of glass, and in that the second lubricating protective layer is formed by allowing a transparent/translucent lubricant to contact the glass of the substrate.
In the present invention, the transparent/translucent lubricant is directly applied to the glass face of the substrate. Therefore, the beam irradiation face can be protected without forming a resin layer thereon, and also to improve the floating stability and the travelling stability of the slider.
The magneto-optical recording medium of the present invention is characterized in that a buffering layer that is made of a transparent/translucent dielectric is further formed between the substrate and the second lubricating protective layer.
Therefore, since the buffering layer, for example, made of an oxide or a nitride, is formed, it becomes possible to reduce the possibility of tilting, warping, etc. of the substrate due to thermal expansion or moisture absorption of the substrate. Moreover, the second lubricating protective layer makes it possible to improve the floating stability and the travelling stability of the slider.
The magneto-optical recording medium of the present invention is characterized in that the transparent/translucent lubricant accounts for 5% by weight to 15% by weight of the lubricating protective layer.
In the present invention, in the case when the transparent/translucent lubricant accounts for 5% by weight to 15% by weight, it is possible to provide better floating stability and travelling stability in the slider. The transparent/translucent lubricant less than 5% by weight causes a reduction in the lubricating property, and that exceeding 15% by weight makes the adhering property to the slider greater, resulting in degradation in the floating stability and the travelling stability of the slider in comparison.
The magneto-optical recording medium of the present invention is characterized in that the above-mentioned transparent/translucent lubricant uses oil at least one selected from the group consisting of fluorine-containing oil, silicon oil and hydrocarbon oil.
In the present invention, oil that is in a liquid state at room temperature (liquid lubricant) and has a superior affinity with a parent-material resin or a base material, such as fluorine-containing oil, silicon oil and hydrocarbon oil that are, for example, ether-modified, alkyl-modified, ester-modified, alcohol-modified or carboxyl-modified, is used as the transparent/translucent lubricant. These materials have a superior chemical adsorptive property to a dielectric layer made of an oxide or a nitride, acrylic resins or glass; therefore, by allowing these to adhere to a substrate made of glass or an acrylic resin, or to a dielectric layer, it becomes possible to extremely improve the lubricant durability of the lubricating protective layer.
Moreover, another objective of the present invention is to provide an optical head device which can improve the floating stability and the travelling stability of a slider-type optical head by forming the slider by using a liquid crystal polymer.
The optical head device of the present invention is characterized by comprising: a slider being allowed to slide or float on or over the surface of a magneto-optical recording medium, the slider being formed by a polymer material containing a liquid crystal polymer; and a light source that emits a light beam onto the magneto-optical recording medium through an objective lens installed in the slider.
In the present invention, the slider, which is injection-molded by using a liquid crystal polymer, is formed into a desired shape with high dimensional precision; therefore, it is possible to provide higher floating stability and travelling stability in the slider. Moreover, as compared with sliders made of ceramics that are used in magnetic disks, this slider is less susceptible to scratches on the disk surface.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.